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BIG PHYSICS, BIG QUESTIONS –

Computer vision algorithms pick out petty crime in CCTV footage

Caught in the act? P-REACT can pick up suspicious behaviour

Alan Thornton/Getty

By Timothy Revell

Petty criminals had better watch out. A computer vision system has been developed that detects suspicious behaviour in CCTV footage as it happens. The system can then alert CCTV operators to intervene, and save the footage in case it is needed for evidence.

Researchers involved in the P-REACT project, which is the work of a consortium of European companies and organisations and is partly funded by a grant from the European Commission, say the surveillance technology could help catch criminals in the act and relieve police of “digital evidence overload” by highlighting video clips most likely to be relevant to investigations.

“If a camera at a gas station picks up suspicious activity, the video footage will be sent to the cloud, people at the gas station will be alerted, and nearby cameras will be told to look out for the criminals too,” says project coordinator Juan Arraiza at Vicomtech, a research foundation in San Sebastian, Spain.

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P-REACT tracks people’s movements to work out whether they’re simply walking along a street, for instance, or doing something dodgy. Its algorithms have been trained on sample scenes of people fighting, chasing someone or snatching a bag. They had to be finely tuned to identify these activities: hugging can look a lot like fighting, for example, while running can be mistaken for giving chase.

Petty criminals

The first tests of P-REACT were run last year in a carefully controlled environment, with actors playing the roles of petty criminals. In this idealised set-up the system reacted flawlessly, catching every play-acted crime – though it is likely to have more difficulty in a real-world scenario where scenes are less predictable. The technology was presented at the International Conference on Imaging for Crime Detection and Prevention in November, with more extensive field trials planned for the future.

Meanwhile, aspects of the technology are already being rolled into tools for use by police.

Dublin-based company Kinesense is developing products that will give police access to CCTV clips selected by the P-REACT system. “One of the biggest challenges police face is digital evidence overload,” says chief technology officer Mark Sugrue. “P-REACT solves this by letting the camera send only important clips.”

Sean Gaines at Vicomtech says P-REACT could also help prevent profiling based on race or age, as the system only analyses movement and is not subject to the conscious or unconscious biases that might influence a CCTV operator’s decisions. “Our algorithms do not take appearance into account, only actions matter,” he says.

Teo de Campos at the University of Brazil says that systems like P-REACT are a useful tool that “help the operator in a surveillance room to focus on relevant cameras or even in relevant regions of images”. Similar systems are probably already in use in some places, he says, but the details are often kept secret.

However, although systems like P-REACT can help pick out unusual behaviour, Marcos Nieto at Vicomtech emphasises that they can’t actually tell if an act is criminal. That particular job should be “left for the human beings”.